1. Field of the Invention
The present invention relates to an ink jet recording apparatus and an ink jet recording head, for executing recording by discharging ink from an ink flow path depositing such ink onto a recording medium.
2. Related Background Art
Among various recording methods employed in the current recording apparatus such as a printer, the ink jet recording method is attracting attention because it is a non-impact recording method almost free from noises at the recording and capable of high-speed recording, and is widely employed as an effective recording method. Recently demand is increasing for color recording or high quality recording utilizing such ink jet recording method, and there is proposed a configuration enabling gradational representation by varying the dot size in order to achieve high image quality. For example there is known a configuration having plural heat generating elements in a liquid flow path and supplying the individual heat generating elements selectively with drive signals from a functional element circuit formed on a substrate, thereby varying the amount of the ink discharged per pixel and enabling gradational recording of an image. Also there is required to record the image with plural inks, resulting in an increase in the number of inks.
In case two or more inks are employed, the amount of the discharged ink and the time required by the vibration of the liquid meniscus to stabilize after ink discharge fluctuate depending on the kind of the ink. The refilling speed becomes no longer constant if the time required by the vibration of the liquid meniscus to stabilize fluctuates. However, in order to achieve recording of high image quality, it is necessary to obtain an appropriate ink discharge amount according to the kind of the ink and to obtain same discharge characteristics (refilling time, discharge speed etc.) regardless of the kind of the ink.
In consideration of the foregoing, the object of the present invention is to provide an ink jet recording apparatus and an ink jet recording head capable of satisfactory recording by realizing substantially constant discharge characteristics for all the liquid flow paths even if inks therein are different in the kinds.
The above-mentioned object can be attained, according to the present invention, by an ink jet recording apparatus equipped with an ink jet recording head provided with a discharge port for discharging ink, an ink flow path communicating with the discharge port, and at least two heat generating elements provided in the ink flow path along the direction thereof, wherein the ink is pigment ink and the recording head comprises drive signal supply means for varying the supply timing of drive signals to the plural heat generating elements for ink discharge in such a manner that the drive signal is at first given to the heat generating element at the side of the discharge port at room temperature and the supply timings at the plural heat generating members become simultaneous or closer thereto with an increase in the temperature of the recording head.
The drive signal may include a preliminary drive signal and a main drive signal.
After the supply timings at the plural heat generating elements become simultaneous with the increase in temperature, the drive signal supply means may reduce the pulse duration of the preliminary drive signal in response to a further increase in temperature.
The present invention is further featured by an ink jet recording apparatus equipped with an ink jet recording head provided with plural discharge ports for discharging ink, plural ink flow paths respectively communicating with the discharge ports, and at least two heat generating elements provided in each ink flow path along the direction thereof, the ink jet recording head comprising a pigment ink discharge portion for discharging pigment ink and a dye ink discharge portion for discharging dye ink, and the ink jet recording apparatus comprising drive signal supply means for varying the supply timing of drive signals for ink discharge to the plural heat generating elements of the pigment ink discharge portion in such a manner that the drive signal is at first given to the heat generating element at the side of the discharge port at room temperature and the supply timings at the plural heat generating members become simultaneous or closer thereto with an increase in the temperature of the recording head.
The drive signal may include a preliminary drive signal and a main drive signal.
After the supply timings at the plural heat generating elements become simultaneous with the increase in temperature, the drive signal supply means may reduce the pulse duration of the preliminary drive signal in response to a further increase in temperature.
The drive signals for ink discharge in the plural heat generating elements of the dye ink discharge portion may be supplied in succession in such a manner that the heat generating element at the side of the discharge port is given the drive signal later.
In the dye ink discharge portion, the supply timings of the drive signals for ink discharge in the dye ink supply portion need not be rendered variable.
The present invention is further featured by an ink jet recording apparatus capable of selectively mounting a first head provided with plural discharge ports for discharging ink, plural ink flow paths respectively communication with the discharge ports, and at least two heat generating elements provided in each ink flow path along the direction thereof and adapted to discharge pigment ink of a desired color, or a second head having a structure same as that of the first head and adapted to discharge dye ink of a color same as that of the pigment ink, the ink jet recording apparatus comprising ID recognition means for recognizing an ID provided on each head, and a ROM having a supply timing table, for each ID, for the drive signals for the ink discharge by the plural heat generating elements, wherein the supply timing table of the ROM is selected according to the ID recognized by the recognition means to vary the supply timings of the drive signals for ink discharge by the plural heat generating elements in each head according to the kind of the ink thereby discharging ink droplets of a substantially constant amount in each head.
The supply timings of the drive signals for the plural heat generating elements for discharging pigment ink are such that the drive signal is at first given to the heat generating element at the side of the discharge port, and the supply timings of the drive signals for the plural heat generating elements for discharging dye ink is such that the drive signal may be given later to the heat generating element at the side of the discharge port.
The first or second head may be capable of discharging ink of a color different from the desired color, and such ink of the different color may be of a same kind.
The ink jet recording apparatus may further comprise drive signal supply means for varying the supply timing of drive signals to the plural heat generating elements of the first head for ink discharge in such a manner that the drive signal is at first given to the heat generating element at the side of the discharge port at room temperature and the supply timings at the plural heat generating members become simultaneous or closer thereto with an increase in the temperature of the recording head.
The drive signal may include a preliminary drive signal and a main drive signal.
After the supply timings at the plural heat generating elements become simultaneous with the increase in temperature, the drive signal supply means may reduce the pulse duration of the preliminary drive signal in response to a further increase in temperature.
The present invention is further featured by an ink jet recording head provided with plural discharge ports for discharging ink, plural ink flow paths respectively communicating with the discharge ports, and at least two heat generating elements provided in each ink flow path along the direction thereof, the ink jet recording head comprising a ROM having a supply timing table for the drive signals for the ink discharge by the plural heat generating elements for compensating (correcting) the change in physical properties of the ink depending on the heat temperature, wherein the supply timings of the drive signals for ink discharge by the plural heat generating elements are varied according to the head temperature based on the supply timing table thereby discharging ink droplets of a substantially constant amount.
The present invention is further featured by a single ink jet recording head provided with plural discharge ports for discharging ink, a discharge port forming member provided with plural discharge ports, plural ink flow paths respectively communicating with the discharge ports, and a heat generating element provided in each ink flow path, the plural ink flow paths including an ink flow path in which ink of a different color is supplied, wherein the discharge port forming member has different thicknesses for the discharge ports for inks of different colors and has a boundary portion between the discharge ports for discharging the inks of the different colors and the thickness of the discharge port forming member is changed at such boundary portion.
The heat generating element may be provided in at least two units in the ink flow path along the direction thereof.
In the ink jet recording head, the discharge amount may be different for each ink color.
The present invention is further featured by a single ink jet recording head provided with plural discharge ports for discharging ink, a discharge port forming member provided with plural discharge ports, plural ink flow paths respectively communicating with the discharge ports, and at least two heat generating elements provided in each ink flow path along the direction thereof, the plural ink flow paths including an ink flow path in which ink of a different color is supplied and the discharge amount being different for each ink color, wherein the ink flow paths have a same length and a same height are different in at least one of the heat generating element, the width of the ink flow path and the thickness of the discharge port forming member for each ink color thereby attaining a desired discharge amount for each color of the ink to be discharged.
The above-described configurations provides advantages, in case of discharging plural inks of different kinds from a single head, of satisfying the discharge characteristics of each heater and obtaining satisfactory recording. Based on these advantages, it is rendered possible to maintain the shape of the common liquid chamber, the area of the hydrophilic area on the face bearing the discharge ports, the distance to the discharge port and the shape of the rear end of the ink flow path regardless of the kind of the ink, thereby achieving a reduction in the manufacturing process and in the manufacturing cost.